A centrifuge, in particular, a so-called high-speed refrigerated centrifuge has been widely used in the experimental laboratory or the routine operation of manufacturing process in which ability for cooling and maintaining the rotor rotating at high speed at a lower temperature (for example, 4° C.) and ability for accelerating or decelerating the rotor in a short time are required. This centrifuge is a device capable of obtaining samples centrifuged by holding a sample placed in tube/bottle to be separated and precipitated on a rotor, accelerating and then stabilizing the rotor set on crown in a chamber to a predetermined rotation number and then decelerating and stopping the rotor.
In a related-art high-speed refrigerated centrifuge, it is usual that the centrifuging time of a sample is not so long and thus it is important to improve the collection efficiency of separated and precipitated material by reducing acceleration/deceleration time of a rotor. Accordingly, it is especially demanded that the acceleration/deceleration time is short. Further, when a sample is separated and precipitated during centrifuging operation, in order to prevent the separated and precipitated sample from being deteriorated due to decrease in biochemical activity and temperature, there is need an ability for accurately retaining the sample held in the rotor at a lower temperature (for example, 4° C.) during centrifuging operation. In addition, small installation space and compact size are also important. Furthermore, since the centrifuge is often used in a quiet ambient environment such as research room or experimental laboratory, it is also important to reduce an operating noise.
Meanwhile, the destination (shipping address) of the centrifuge is worldwide, and thus, the power situation varies for each country. For this reason, in related-art, the centrifuge is configured to cover voltage/frequency/power supply capacity of power sources by one design specification. In a general configuration of a product commercially available from the present applicant, a motor for accelerating/decelerating a rotor is subjected to a variable speed control by an inverter and both a compressor motor and a radiator fan of a cooling unit for holding a sample at a lower temperature are subjected to ON-OFF control by a single-phase induction motor.
A technology of using a variable speed compressor of an inverter control type has been proposed in JP-A-H07-246351. The technology disclosed in JP-A-H07-246351 has a configuration that the current supplied from the power supply or returned to the power supply forms a current waveform in which the power factor is high and the harmonic current is reduced, when a motor for rotationally driving the rotor is subjected to the power running and the power regeneration operation. Further, the technology disclosed in JP-A-H06-170282 is so configured that the rotation number of a cooling fan in a region where the power frequency supplied is 60 Hz is reduced to be consistent with the rotation number thereof in a region where the power frequency is 50 Hz and the noise level of the cooling fan generated due to the change of the power frequency is not fluctuated. The technology disclosed in JP-A-H05-228400 relates to a centrifuge for controlling ON-OFF of a compressor motor of a cooling unit. In this centrifuge, a bypass pipe connecting a high-pressure side pipe and a lower-pressure side pipe and a switch are provided. As the compressor is stopped, the switch is opened to eliminate the pressure difference between the high-pressure side pipe and the lower-pressure side pipe in a short time and thus a pressure condition required for restart of the compressor can be achieved.